Mode of action: inhibition of androgen receptor function--vinclozolin-induced malformations in reproductive...

Area of Science:

• Environmental Toxicology
• Reproductive Toxicology
• Endocrinology

Background:

• Vinclozolin is a widely used fungicide with known adverse effects in rodents.
• Observed effects include Leydig cell tumors, accessory sex gland atrophy, and male urogenital tract malformations.
• These effects are linked to the disruption of the androgen receptor (AR) pathway.

Purpose of the Study:

• To evaluate the Human Relevance Framework (HRF) for noncancer health effects of vinclozolin.
• To assess the plausibility of the animal mode of action (MOA) for vinclozolin-induced reproductive malformations in humans.

Main Methods:

• Review of toxicological studies and targeted research on vinclozolin.
• In vitro and in vivo studies examining the binding and inhibition of rat and human androgen receptors by vinclozolin and its metabolites (M1, M2).
• Analysis of androgen-dependent gene expression changes in rat prostate tissue following vinclozolin exposure.

Main Results:

• Vinclozolin and its metabolites (M1, M2) inhibit both rat and human androgen receptor function.
• Exposure to other AR antagonists, like flutamide, results in similar adverse outcomes.
• Direct evidence shows vinclozolin alters androgen-dependent gene expression in the rat prostate.

Conclusions:

• The androgen receptor-mediated mode of action is central to vinclozolin's toxicity.
• Kinetic and dynamic factors suggest high confidence in the human relevance of the animal MOA.
• Vinclozolin-induced male reproductive tract malformations are highly plausible in humans.